Ramblings on our journeys exploring and questioning the validity of "established" scientific "fact."

Tuesday, September 1, 2009

SF Marathon Part II: So why so much slower after 26 years?

I was actually pretty happy with my performance, since my trail ultra times have been much slower, and I wasn’t too confident how I would hold up to all that pavement running. I was also very happy just to be able to do the event, grateful that my 53-year old body, despite its nagging aches and pains, is holding up as well as it is. But why am I slower than I was 26- 27 years ago? Well aging is the obvious excuse, but what does that mean, and is it in any way correctable? Does that mean I have less muscle mass, less strength to work with? Does that mean that my heart is weaker, or just slower? Does that mean my muscles and limbs have lost elasticity and/or I have reduced running economy now? Is my higher blood pressure putting too much load on my heart? Do I have endothelial dysfunction and the muscles are being starved (relatively) of the blood flow they need? Or can it all be attributed to increased weight?

I subsequently ran several other marathons during that time period: Summit Marathon- from Los Gatos to Soquel (across the Santa Cruz mountains, another 3:45 - it was tough!), Oakland and Avenue of the Giants. I tried (and failed) to qualify for Boston at Oakland (the qualifying time was 3:20 at the time, but my calf froze up so badly during the cold rain of that race that I had to back off the pace) for a 3:27. Avenue of the Giants was a 3:34, perhaps still overly cautious with the calf muscle. Still, I was at the point in my mid twenties where sub 3:30 was quite doable. I suppose the other piece of evidence I have is that a couple of years later, after starting grad school, I talked a bunch of other students into trying a marathon (Shamrock Marathon at Virginia Beach). I thought I had prepared much the same as before, training in the hills of Charlottesville, but only managed a 4:15. Maybe there was something magical about that early training on the Bay Area hills…

It’s possible that I stumbled upon a useful training program back in 1981-82, where my usual run was about 5.5 miles on some flat but also some pretty tough hills (the Dish loop). It’s possible that I was just lucky and managed to train hard enough without injury long enough to make good progress. It was all very intuitive- I just trained by how I felt on any given day. It’s possible that the bicycle commuting I did added some extra fitness. It’s all still a mystery to me. It’s also possible that I was still significantly undertrained if I wanted to know what my real potential could be. Given what I know about my training at the time in comparison with what I read about now, it seems that I should have been able to progress even further, perhaps to 3:15, maybe less, though I doubt that I had the potential to do much better than 3 hours.

A very rough calculation/guesstimate of my VO2max based on performances from my mid-twenties is 45 ml/min/kg (based on a 7:57 minute per mile marathon pace), with the caveats that 1) this is not the correct way to determine VO2max of course, 2) I could probably have gone at a faster pace had I trained better and not gotten injured, and 3) my VO2max in 2009 could be very different from my estimated VO2 max from 1983, but this is the best data I have at the moment. In other words, I haven’t sprung for a proper test, so this estimate will have to do for now. This number is not merely imagined, but is based on a chart in Noakes’ book "Lore of Running" where various paces are correlated with weight normalized VO2max values. Having a good VO2max is helpful in achieving good running performance, but it is well known that being able to sustain a higher percentage of your VO2max effort is more influential on running performance than VO2max itself. Superior running economy and other nebulous factors are also important in determining who is actually faster. Noakes discusses these quite a bit in his book. See also Lyle McDonald's post for more discussion about predictors of endurance performance, and VO2 max in particular, or the extensive writings on Alan Couzen's blog .

A correlation to of this VO2max chart with marathon paces to my current values would look something like this: as of race day, I weighed about 144* lbs (65.5 kg); in my marathon running mid-twenties I (think I) weighed about 125 lbs (56.8 kg). Assuming nothing else fundamental has changed, in absolute terms, I should have the heart and lungs and leg muscles etc for a VO2max of 2556.8 ml/min (multiplying by the 56.8 kg). Dividing by my now increased mass, that yields a VO2max of 39.0 ml/min/kg and a predicted marathon pace of 9:08 per mile, or about 4 hours. This happens to be closer to my predicted Yasso 800 marathon time of 4:10 than what I actually did in July (4:31), but still seems to indicate I should be able to do close to a 4 hour marathon if the only adjustment to VO2max was added weight. My 2009 performance (10:13 minute per mile marathon pace) would suggest a VO2max of ~34 ml/min/kg. Maybe this wasn’t a best effort due to not being able to stretch out a bit more in the first half, and also by the fact that I had no muscle soreness the days after, that would seem to suggest I didn’t push the pace as much as I maybe could have. Of course, VO2max doesn’t tell the whole story- there are many accounts of people being faster without having a higher VO2max. It’s also possible that I have less lung capacity due to past bouts with pneumonia- the x-rays do show some scarring.

Of course the most likely explanation is that I’m just poorly trained/more cautious now. According to “Hadd’s Take on Distance Training” (skip ahead to part 6 if you want to see how to calculate marathon heart rate (HR) and training HR), marathon HR should be 15 – 20 bpm slower than max HR. In other words, if properly trained and motivated, you should be able to maintain an effort for marathon distance at 15 – 20 bpm slower than max HR, but it shouldn’t feel uncomfortable. According to this calculation, my marathon HR should be more like 155 than 145. That HR for me right now translates into about a 9:00 – 9:10 pace- much closer to the Yasso 800 predicted time, and in good agreement with my estimates from VO2max calculations, but still pretty difficult to maintain.

So why didn’t I run nearer 155? Good question, don’t really know. Some of it is a sense of cautiousness, that I maybe shouldn’t overstress myself, at least not pushing too much. Running at a HR of 155 feels pretty hard to me these days- it’s not hard enough to be reduced to frantic panting, but it feels too hard to maintain for more than a few miles. Perhaps I need to follow more of Hadd’s suggested training and develop my aerobic potential as far as I can and then see how it goes. It’s surprisingly hard to do though- the natural inclination is to run at a pace that feels good- that pace tends to be slightly anaerobic though, especially when rested and feeling good, but not really sustainable for miles and miles.

Another posting on Chuckie V’s site addresses this further. This post basically says that lots of mileage is what makes for superior runners, and points out that the qualifying times for Boston have been eased up over the years because people are training differently, relying on “quality” higher intensity workouts rather than higher mileage. Alan Couzens also addressed this recently, pointing out that research supports the idea that aerobic adaptation in slow twitch fibers is linear with increasing exercise stimulus, suggesting that easier training for several hours per day could provide further increases in training effectiveness. This is not true for threshold/”high intensity” training, the improvements from which maxed out in some studies at about 1 hour. The good news is that you don’t have to kill yourself with exhausting stressful training to see the benefit, and it also accrues over years, even decades! Of course, there is a place for higher intensity training, to increase lactate threshold and sharpen up your speed, or for fun. Anyone who runs on hilly terrain can hardly avoid some higher intensity work on occasion anyway, but the bulk of the training does not have to be “hard.” This training philosophy is not currently fashionable, and I may not be able to manage much more mileage than I currently do anyway (40-65 miles per week), but I can try.

There is a pretty clear correlation of age with heart rate, and it seems that a slowed heart rate should have an effect on my slower performance as well. At this point it’s hard to know since I don’t know what HR numbers I was dealing with in my youth (though I'm sure they were much higher than now), and since my resting HR (and max HR) keeps dropping now. But according to the calculation above, the real limitation resulting in my slower performance is my excess weight, i.e., if I could maintain my marathon HR (a big IF) I would perform at a level that is scaled down by my greater mass. So theoretically, if I lost down to 125 lbs again, I should be able to perform as well as I could in my twenties? This seems unlikely, but worth the experiment. I’ll keep working on it.

No comments:

About Us

Two scientists (doctorates in Biophysical Chemistry and Gas Dynamics, respectively), married (to each other) and currently practicing patent law (as patent attorney and agent respectively). Wide-ranging knowledge and interests; continuing to discover that at least half of what they learned in school is wrong.